The fiery July 26 wreck on the Taconic State Parkway left eight people dead.

FLORAL PARK, N.Y. (AP)  Diane Schuler was a devoted mother admired for her competence, ease with children and sense of humor. Never, her family said, had there been a more responsible and trusted friend or caregiver.

So far, no one can pinpoint why Schuler, 36, drove the wrong way on a familiar suburban New York parkway for nearly 2 miles before slamming head-on into another vehicle, killing herself and seven others.

State police investigating the fiery July 26 wreck on the Taconic State Parkway are examining a phone call Schuler made to her brother shortly before the crash. She was taking her two children and three nieces home from an upstate camping trip at the time.

A medical examiner is digging deeper for answers after ruling that Schuler didn't have a heart attack or stroke behind the wheel, and plans further testing to determine whether she had signs of an advanced diabetic condition.

The crash — the worst in the parkway's 75-year history — killed Schuler, her 2-year-old daughter and three nieces ages 5, 7 and 8, as well as three Yonkers men in the SUV hit by her minivan. Only Schuler's 5-year-old son survived.

"I have never heard of eight people being killed in an accident of this kind," said Peter Plante, a retired Connecticut state trooper and traffic accident reconstruction expert. "It's almost as if it were a perfect storm of circumstances with so many people in each vehicle."

Douglas Hayden, an attorney and spokesman for the Long Island family, declined comment on the investigation Friday.

The accident happened on a sunny and clear summer afternoon in Briarcliff Manor on a route from upstate New York to Long Island that Schuler had driven many times before. She found herself going south in the northbound lanes as motorists sought in vain to get her attention; six drivers called 911 before the collision.

One of the few clues state police have is a telephone conversation between Schuler and her brother, Warren Hance, the father of the older girls who died. About a half-hour before the wreck, Schuler called Hance at his home in Floral Park and seemed disoriented, saying she was having trouble seeing. Her husband had left the campground earlier Sunday for a fishing trip, police said.

At one point, Hance's 8-year-old daughter Emma took her aunt's cellphone and spoke to her father, indicating the van had just crossed the Tappan Zee Bridge south into Westchester County. Hance then told his sister to stay put and he would drive from Long Island to meet her, instructions she disregarded.

Family friend Lisa Acosta said the Schulers camped almost every weekend at the same upstate park, and said Schuler knew the route so well she could have driven it blindfolded.

"I don't understand," said Acosta. "It's a really, really sad thing."

Schuler's cellphone was left at the parking area south of the bridge, where she last spoke to her brother. A motorist found it later in the day.

After forensic pathologists ruled out a stroke, aneurysm or heart attack, Dr. Kunjlata Ashar, deputy medical examiner for Westchester County, said she would test Schuler's eye fluid for evidence of heightened blood sugar levels, a possible sign of ketoacidosis.

The American Diabetes Association says ketoacidosis is a life-threatening condition that can cause shortness of breath, nausea and confusion.

"People just don't have a hypoglycemic crisis out of the blue," said Baden, who has been an expert witness in cases involving celebrities such as John Belushi, O.J. Simpson, Phil Spector and David Carradine. "The family would know right away if this woman had issues with diabetes."

Baden said other toxicology testing results, due within four to six weeks, could yield some answers.

"They didn't see anything in the autopsy that could account for this behavior," he said. "Now they are going under the microscope to see if they can find something."

Ashar said her testing also has ruled out carbon monoxide poisoning as a possible cause.

Except for issuing a written statement about the victims, the Schuler and Hance families have chosen to grieve privately.

"Diane was an accomplished working mother who balanced her responsibilities with grace; she always put her children before any other priorities," the family statement said.

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